Many tobacco substitute smoking materials have been proposed through the years, especially over the last 20 to 30 years. These proposed tobacco substitutes have been prepared from a wide variety of treated and untreated materials, especially cellulose based materials. Numerous patents teach proposed tobacco substitutes made by modifying cellulosic materials, such as by oxidation, by heat treatment, or by the addition of materials to change the properties of the cellulose. One of the most complete lists of these substitutes is found in U.S. Pat. No. 4,079,742 to Rainer et al.
Many patents describe the preparation of tobacco substitute smoking materials from various types of carbonized (i.e., pyrolyzed) cellulosic material. These include U.S. Pat. No. 2,907,686 to Siegel, U.S. Pat. No. 3,738,374 to Bennett, U.S. Pat. Nos. 3,943,941 and 4,044,777 to Boyd et al., U.S. Pat. Nos. 4,019,521 and 4,133,317 to Briskin, U.S. Pat. No. 4,219,031 to Rainer, U.S. Pat. No. 4,286,604 to Ehretsmann et al., U.S. Pat. No. 4,326,544 to Hardwick et al., U.S. Pat. No. 4,481,958 to Rainer et al., Great Britian Pat. No. 956,544 to Norton, Great Britain Pat. No. 1,431,045 to Boyd et al., and European Patent Application No. 117,355 by Hearn, et al. In addition, U.S. Pat. No. 3,738,374 to Bennett teaches that tobacco substitutes may be made from carbon or graphite fibers, mat or cloth, most of which are made by the controlled pyrolysis of cellulosic materials, such as rayon yarn or cloth.
Cigarette-type smoking articles which preclude the introduction of combustion gases into the mainstream aerosol are known. Generally this is accomplished by providing a chamber or passageway for the mainstream aerosol source and a physically separate fuel, the mainstream aerosol being prevented from mixing with the combustion products produced by the burning fuel.
For example, Ellis et al. in U.S. Pat. No. 3,258,015, describe several embodiments of proposed cigarette-like smoking articles having an axially extending aerosol/nicotine releasing tabular member, typically surrounded by the tobacco fuel. The physical arrangement of this system precluded entry of any of the combustion products into the tubular member which carried the mainstream aerosol. Similar propsed devices are described in Synectic British Pat. No. 1,185,887.
Likewise, in certain embodiments of Moses, U.S. Pat. No. 3,516,417, cigarette-like smoking articles are described wherein tobacco is burned to generate heat, and this heat is used to warm air which is delivered to the user. There is no contamination of the heated air by the combustion products of the burning tobacco.
Similarly, in Steiner, U.S. Pat. No. 4,474,191, proposed smoking articles are described in which, except for a brief temporary period at the moment of lighting, combustion gases are not delivered to the user. The mainstream aerosol comprises volatile and/or sublimable materials disposed within a channel separated from the heat source.
Cigarettes and cigarette-like smoking articles have also been provided with draft passages or similar tubular members extending longitudinally through the fuel, but generally such articles do not exclude combustion products from the mainstream aerosol.
For example, Helm, in U.S. Pat. No. 2,349,551, describes a cigarette modified to have disposed centrally within the tobacco charge, an impervious draft tube, through which combustion gases will pass, following the path of least resistance. Bell et al. in U.S. Pat. No. 3,349,776 describe a low temperature cigarette having an axially extending draft column. Ellis et al., in U.S. Pat. No. 3,356,094, describe an improvement over their eariler patent (supra) wherein the tubular member became frangible upon exposure to heat. Levavi, in Canadian Pat. No. 687,136, described proposed cigarettes with tubes, some of which were metal and some of which burned slowly, for controlling the amount of tar and nicotine delivered to the user.
Similarly, Vega, in U.S. Pat. No. 3,674,036, describes a cigarette-like smoking article having a centrally located perforated tubular core member which permits fresh air passage through the tobacco, thereby slowing down the combustion. Thorton, in U.S. Pat. No. 3,614,956, describes a smoking article comprising a tobacco fuel having an axially disposed absorbent core which serves to absorb noxious materials from the combustion gases. The core may be separated from the tobacco fuel by means of a ceramic sleeve.
Likewise, Selke et al. in U.S. Pat. No. 3,756,249, describe a smoking article such as a cigarette which contains an axially extending tube which serves as an air passageway during smoking. Hunt, in U.S. Pat. No. 3,863,644, describes a smoking article having two or more tube-like chambers of different length, which chambers provide a programmed air ventilation effect during the smoking of the article. Yatrides, in U.S. Pat. No. 3,905,377, describes smoking articles provided with a blind conduit allowing the passage of air to the tobacco, thereby increasing the condensation of toxic vapors in the combustion gases.
Kaswan, in U.S. Pat. No. 4,027,679, describes a cigarette having disposed therein a ceramic or metallic smoke vector, open at the lighting end and sealed at the mouth end. This vector is said to reduce the draw heat of the article, thereby reducing the amount of pyrolysis products in the aerosol.
Bolt et al., in U.S. Pat. No. 4,340,072, describe a proposed smoking article having a fuel rod with a central air passageway and a mouthend chamber containing an aerosol forming agent. The fuel rod preferably is a molding or extrusion of reconstituted tobacco and/or tobacco substitute, although the patent also proposes the use of tobacco, a mixture of tobacco substitute material and carbon, or a sodium carboxymethylcellulose (SCMC) and carbon mixture. The aerosol forming agent is proposed to be a nicotine source material, or granules or microcapsules of a flavorant in triacetin or benzyl benzoate. Upon burning, air enters the air passage where it was mixed with combustion gases from the burning rod. The flow of these hot gases reportedly ruptures the granules or microcapsules to release the volatile material. This material reportedly forms an aerosol and/or is transferred into the mainstream aerosol. Similar articles are described in FIG. 4 of the Moses patent, supra using a tobacco fuel and in the Hearn European Patent, supra, using a carbonized fuel.
Burnett et al., in U.S. Pat. No. 4,391,285, describe proposed smoking articles comprising a high density combustible tobacco containing fuel having at least one passageway extending longitudinally therethrough. This passageway may contain an easily ignitable air permeable plug which may optionally contain thermally releaseable flavorants.
Clearly, despite decades of interest and effort, none of the aforesaid smoking articles have been found to be satisfactory as a cigarette substitute. Indeed, despite extensive interest and effort, there is still no smoking article on the market which provides the benefits and advantages associated with conventional cigarette smoking, without delivering considerable quantities of incomplete combustion and/or pyrolysis products.